Electromagnetic relay

ABSTRACT

Improved contact structure for a relay. In a double-throw version, two spaced helical springs for each pole are partially compressed between a spring support and the movable contact to provide initial contact pressure. A contact support overlies the movable contact and screws secure all of these parts on top of a rockable armature. In a single-throw version, normally open or normally closed, only one helical compression spring per pole nearest the closing end of the contact may be used to provide initial contact pressure; and a dummy load is provided at the non-closing end of the movable contact to afford the same operating characteristics in the single-throw relay as in the double-throw relay since the operating mechanism uses an electromagnet and a permanent magnet to give equal contact forces at both ends of the throw.

is] 3,693,120 [451 Sept. 19, 1972 Primary Examiner-Harold Broome Attorney-Hugh R. Rather et al.

[57] ABSTRACT Improved contact structure for a relay. In a doublethrow version, two spaced helical springs for each pole are partially compressed between a spring support and the movable contact to provide initial contact pressure. A contact support overlies the movable contact and screws secure all of these parts on top of a rockable armature. In a single-throw version, normally open or normally closed, only one helical compression 1 spring per pole nearest the closing end of the contact may be used to provide initial contact pressure; and a dummy load is provided at the non-closing end of the movable contact to afford the same operating characteristics in the single-throw relay as in the doublethrow relay since the operating mechanism uses an electromagnet and a permanent magnet to give equal contact forces at both ends of the throw.

10 Claims, 8 Drawing Figures Barr Spellman, Milwaukee, both of Wis.

[73] Assignee: Cutler-Hammer, Inc., Milwaukee,

Wis.

June 23, 1971 [21] Appl. No.: 155,793

....335/128, 335/179 51/06 .335/128, 136, 202, 132, 17, 335/129, 106, 179; 200/166 H, 67 F, 6 B, 67 C References Cited UNITED STATES PATENTS 3/1942 Seeley.......................335/128 9/1961 Didier........................335/l36 United States Patent Quaal et al.

154] ELECTROMAGNETIC RELAY [72] Inventors: John A. Quail, Wauwatosa; Gordon 22 Filed:

[58] Fie1dofSearch.......

il I JV li r Fi :MD in II filial/aid PATENTEDSEP 1 9 I972 SHEET 1 BF 3 PAYIENIEMP a a 1912 SHEET 3 [If 3 BACKGROUND OF THE INVENTION Helical compression springs have been used for biasing contacts heretofore. Such springs have been used in connection with stationary contacts for providing resiliency when the movable contact engages therewith. Such springs have been used also in connection with movable contacts, primarily to provide contact pressure to straight-line motion bridging contacts and the like.

While such contact spring arrangements have been useful for their intended purpose, this invention relates to improvements in rocking contact structures involving the use of helical compression springs in electromagnetic relays.

SUMMARY OF THE INVENTION This invention relates to improved rocking'contact structures of the single-throw and double-throw type.

An object of the invention is to provide improved rocking contacts for an electromagnetic relay.

A more specific object of the invention is to provide in an electromagnetic relay of the type that uses a permanent magnet to afford equal contact forces at both ends of the armature throw, improved double-throw contacts and dummy-loaded single-throw contacts of the normally open or normally closed types.

Another specific object of the invention is to provide in a relay having equal contact forces at both ends of its throw, improved single-throw and double-throw contacts requiring minimum substitution of parts therefor.

A further specific object of the invention is to provide improved single-throw and double-throw contacts for an electromagnet relay that are simple in construction and effective in operation.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a three-pole doublethrow electromagnetic relay in which the invention is used;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 3 to show a side view of the movable doublethrow contacts;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2 to show a front view of the movable contacts;

FIG. 4 is an exploded isometric view of the armature and movable contact structure of the three-pole double-throw relay of FIGS. 1-3;

FIG. 5 is an isometric view of a three-pole singlethrow electromagnetic relay in which the invention is used;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 7 to show a side view of the movable singlethrow contacts;

FIG. 7 is a cross-sectional view taken along line 7 7 of FIG. 6 to show a front view of the contacts; and

FIG. 8 is an exploded isometric view of the armature and movable contact structure of the three-pole singlethrow relay of FIGS. 5-7.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-4, there is shown a first embodiment of the invention including double-throw contacts. Three-pole contacts have been shown for purposes of illustrating the invention.

As shown in FIG. 1, the relay comprises an insulating base 2 having a plurality of terminals mounted thereon for connecting the relay to an external circuit. These terminals comprise a first row of three terminals 4 connected to respective stationary contacts, a second row of three terminals 6 connected to respective stationary contacts, and a third row of three terminals 8 connected to respective movable contacts. The latter three terminals 8 are mounted on a raised portion 2a of the base extending along the center thereof, this raised portion providing space within the relay for connector conductors or pigtails hereinafter described in connection with FIG. 2. These three rows of terminals of three terminals each are arranged so that the terminals for the stationary contacts are on each side and the terminals for the movable rocking contacts are in the middle.

In addition to the above terminals, there is provided a pair of terminals 10 at one end of the base connected to respective stationary contacts of a single-pole dou ble-throw auxiliary switch. A third terminal 12 on a partially raised portion of the base is connected to the movable contact of such auxiliary switch.

The remaining two terminals 14 are on the opposite end of the base located symmetrically relative to terminals l0 and are connected to the relay operating coil.

The relay mechanism including its operating magnet and contacts is mounted to the base on the lower side thereof. A metal housing 16 surrounds the relay mechanism and is secured to the base by four screws extending down through holes in bosses 2b at the corners of the base. The housing is sealed to the base by an O-ring seal 18 seated in a groove in the base as shown in FIGS. 2 and 3 against which the upper edge of the housing is pressed when the four screws are tightened. A pair of mounting tabs 16a are provided on the front and back of the housing flush with the bottom. These tabs are provided with holes as shown in FIGS. 1 and 2 for receiving mounting screws, bolts, or the like.

The relay mechanism is put together in three subassemblies, namely, (1) the operating magnet subassembly, (2) the armature and movable contacts subassembly, and (3) the base and stationary contacts subassembly. These three subassemblies are then connected together by connecting the wires to the terminals and mounting the magnet to the base by four screws.

The base and stationary contacts subassembly comprises the aforementioned terminals mounted onto the base as shown in FIGS. 1-3. Terminals 6 are molded into the insulating base and extend through the base with their upper, external ends being threaded to receive washers and nuts for connection of electrical wires, and their lower internal ends having adjustable stationary contacts 6a formed thereon. These stationary contacts are made adjustable by having threaded shanks entering tapped bores to to afford adjustment of the contact tips up or down by turning thereof. In the embodiment of the invention shown in FIGS. 1-3, stationary contacts 6a are arranged to be normally open with respect to the movable contacts hereinafter described.

Terminals 4 of this subassembly are similar to terminals 6 just described and are molded into the base and provided with similar adjustable stationary contacts 4a below the base so as to be within the relay housing. These stationary contacts 4a are arranged to be normally closed with respect to the movable contacts as shown in FIG. 2.

Terminals 8 of this subassembly are also molded into the base at its central raised portion and are provided with threads at their upper, external ends to receive washers and nuts for attachment of electrical conductors in the same manner as terminals 4 and 6. The lower, internal ends of these terminals 8 are provided with means for connecting movable contact connector wires or pigtails. For this purpose, the lower ends of these terminals may be provided with tapped bores for receiving screws for securing flexible connectors thereto to connect the three movable contacts 22 to the respective terminals 8.

The operating magnet and movable contacts subassembly comprises a magnetic frame 24 and an operating coil 26 as shown in FIGS. 2 and 3. This frame 24 comprises a generally E-shaped structure formed from an L-shaped member 24a of magnetizable material, a round core 24b extending up from member 24a, and a permanent magnet member PM in spaced parallel relation to core 24b and to the vertical part of member 24a. This permanent magnet is held in place by a cross-bar 28 overlying it and a pair of screws 30 extending through frame member 24a along opposite sides of this permanent magnet into threaded engagement with the cross-bar. Coil 26 surrounds core 24b and a plate 32 is secured to the upper end of the core to hold the coil in place and has a pair of short studs on its upper surface to provide a pivot for the armature as hereinafter described. Coil terminals 26a are connected by a pair of wires to terminals 14, respectively.

For securing this operating magnet and movable contacts subassembly to the base, the base is provided with four downwardly extending, integrally molded studs 2c shown in FIG. 3 having tapped holes in the lower ends thereof for receiving attaching screws. Also, the magnet subassembly is provided with two pairs of laterally extending arms having screw holes therein overlying studs 20. Two of these arms 24c extend laterally from the vertical part of frame member 24a shown in FIG. 3. The other two of these arms are the ends of the crossbar 28.

The armature and movable contacts subassembly is shown assembled in FIGS. 2 and 3, but is shown more clearly in the exploded view in FIG. 4. As shown in FIG. 4, armature 34 is a generally rectangular flat piece of magnetizable metal bent slightly at its center so that the two ends are raised and the transverse line at the center forms a pivot for rocking movement of the armature when resting on a flat surface. A pair of holes 34a are spaced apart on the aforesaid transverse center line to receive the aforementioned pivot studs integral with plate 32 for holding the armature in correct registration on top of the operating magnet and allowing it to rock and actuate the movable contacts carried thereon. Notches 34b may be provided at the opposite ends of the armature for retaining non-magnetic shims that prevent the armature from sticking to the poles of the magnet. The armature is further provided with four tapped holes 340 thereon for receiving screws that attach the spring support and contact carrier moldings thereto.

As shown in FIG. 4, movable contact clamping means comprising a spring support 36 which may be a molding of insulating material and having its lower surface formed at an obtuse angle complementary to the obtuse angle on the upper surface of the armature is placed on top of the armature. This spring support 36 is provided with three pairs of shallow depressions 36a, two for each movable contact, with the depressions of each pair being on opposite sides of a center ridge 36b. As will be apparent, these pairs of depressions serve to retain respective pairs of movable contact biasing, helical compression springs 38 that are placed on top of this spring support. Three movable contacts 22 are then placed on top of the pairs of contact biasing springs 38. Finally, this clamping means comprises contact support 40 placed on top of the movable contacts and held down to partially depress the springs while four screws 42 are inserted through holes in contact support 40 and spring support 36 and turned into tapped holes 34c in the armature to complete the subassembly.

Spring support 36 is also provided with four partial, stepped dividing walls 360, two on each side, equally spaced so as to form spaces for the movable contacts and to divide the contacting end portions thereof and lengthen the electrical creepage paths therebetween. These walls also form ridges fitting into underside grooves 40a in contact support 40 to provide interfitting positioning of the contact support on the spring support. In addition, spring support 36 is provided with forward and rear upwardly extending walls 36d to the level of the slightly higher end portions of the dividing walls 36c to enclose the opposite ends of the movable contacts.

Referring now to contact support 40 in FIG. 4, it will be seen that it is an insulating molding having generally two spaced parallel laterally extending bars 40b that are connected by four transverse bars consisting of a pair of spaced, like middle bars 40c and a pair of like ends bars 40d, one on each of the left and right ends. These four transverse bars are substantially equally spaced from one another to provide three spaces therebetween for the three movable contacts of the three-pole relay. The opposite end portions of the two spaced middle bars 400 are provided with the aforementioned underside grooves 40a shown in FIGS. 3 and 4 for receiving dividing walls 36c of the spring support 36. These spaced middle bars 400 are also each provided with an underside transverse groove 40e shown in FIGS. 2 and 4 at the center thereof with the grooves on the two middle bars being in alignment to receive ridge 36b of the spring support. These interfitting parts provide registration between the contact support 40 and the spring support 36 and additionally afford three compartments, open at the top, in which the three movable contacts are held. The ends of movable contacts 22 are provided with lateral ears 22a near the contact tips to impart a good hammer blow in breaking contact welds. These ears are engaged by bars 400 and 40d of the contact support each time the armature is operated. When closing on motor load inrush, which is approximately five times rated current, there is generally some welding at the contact tips as a result of arcing from contact bounce and subsequent closing on molten contact material. For good non-welding efficiency, imparting a sound hammer blow on opening is necessary.

When the movable contacts and springs have been assembled onto spring support 36 and contact support 40 has been placed thereover and screws 42 are tightened, the two lateral bars 40b press down on the movable contacts as shown in FIG. 2 to provide an initial compressive force on springs 38. Thus, these springs bias the movable contacts upwardly against lateral bars 40b. In this subassembly, end bars 40d of the contact support provide partial walls for the left and right sides of spring support 36 as best shown in FIG. 3.

Contact support 40 is additionally provided with means for supporting the movable contact of a singlepole double-throw auxiliary switch. This means comprises a pair of lateral extensions 40f on contact support 40, as shown in FIGS. 3 and 4, onto which a generally V-shaped movable contact is secured by a rivet or the like as more fully shown and described in copending application Ser. No. 155,853, filed June 23, 1971. Contact support 40 is made symmetrical for ease of assembly either way even if only one auxiliary switch is intended to be used.

As shown in FIG. 2, when the relay is in its unoperated condition, terminals 4 are in electrical connection to terminals 8 through the respective normally closed contacts of the relay. Under this condition, permanent magnet PM holds armature 34 in contact with cross bar 28 that forms one pole piece for the magnet. Consequently, the left end of each of the movable contacts is pressed against its respective stationary contact 4a. This causes the left end of each movable contact to move against the force of its springs 38 and to separate slightly from bar 40b of contact support 40 for increased wear allowance. Also, the permanent magnet provides a contact force between contacts 22 and 4a substantially equal to the contact force between contacts 22 and 6a afforded by energization of the coil.

Now when the operating coil is energized to operate the ,electromagnet, the armature rocks counter clockwise in FIG. 2 to bring the left end thereof down against its pole piece 24d, shown in FIGS. 2 and 3, and to lift its right end from the pole piece formed by cross bar 28. As a result, the left end of each movable contact separates from its respective stationary contact 4a and the right end thereof is closed against its respective stationary contact 6a. This causes the right spring 38, FIG. 2, of each movable contact to be compressed and causes the movable contact to separate slightly from the right bar 40b for increased wear allowance. As a result, terminals 8 become connected to respective terminals 6.

The use of the permanent magnet in connection with the electromagnet affords equal contact forces at both ends of its armature throw. This afiords equal electrical and vibration and shock resistance at both ends of the throw. To preserve these characteristics in the singlethrow version, a dummy load is provided in place of each stationary contact that is not needed therein as hereinafter described.

The single-throw version of the relay shown in FIGS. 5-8 requires a base 44, a spring support 46 and movable contacts 48 that are modified, and three of the six springs 38 may be omitted, but otherwise common parts may be used in the two different versions.

As shown in FIG. 5, base 44 differs in that three of the terminal positions are molded closed because terminals 4 and their respective stationary contacts 4a are not used. Instead, dummy loading studs 440 are integrally molded on the underside of the base as shown in FIGS. 6 and 7. The inactive ends 48a of the movable contacts, FIGS. 6 and 8, bear against the lower ends of these projections to provide loading on the operating magnet during the deenergized condition of the operating magnet in a similar manner to the normally-closed stationary contacts of the double-throw version. As will be apparent, the single-throw version has normallyopen contacts that close when the magnet is energized.

While a normally closed contacts version of singlethrow relay has not been shown, it will be apparent that it can be assembled from the same parts as the normally open contacts version by turning the magnet including its armature around degrees so that in FIG. 6 the permanent magnet is at the left side instead of at the right side. As a result, the left air gap will be closed and the right air gap of the armature will be open and the movable contacts will engage the stationary contacts. Also, the inactive ends of the movable contacts will be separated from dummy load studs 44a.

In this single-throw version as shown in FIG. 8, the movable contacts 48 have a normal contacting structure at the right end thereof for engagement with the stationary contacts 6a. Their other inactive ends do not include the contacting structure, and have sufficient flat length to engage dummy load studs 44a.

The contacting ends of these movable contacts have ears 48b to which a hammer blow is imparted by transverse bars 400 and 40d when the armature pivots to open the contacts in the event there is any sticking or welding.

There is another way of changing from the normally open contacts version shown in FIG. 6 to a normally closed contacts version. If in this case it is desired that the terminals are numbered on the base, and that terminals 6 and 8 will uniformly be normally open terminals and terminals 4 and 8 will always be normally closed terminals, then it is necessary to provide a different base for the normally closed contacts version. On such different base, terminals 4 and 8 will be provided and terminals 6 will be left out. Also, the dummy load studs 44a will be at the right side, as viewed in FIG. 6, rather than the left side. In addition, for this normally closed contacts version the movable contacts will be assembled reversed, that is, with their contacting tips at the left and their inactive ends 48a at the right as viewed in FIG. 6. In either way, however, it will be apparent that only minimum substitution of parts is involved in assembling a relay of a different version.

In this single-throw version as shown in FIG. 8, spring support 46 is like that in the double-throw version except the rear side has been cut off, or molded minus the same. This cutoff part starts at the partial dividing walls so that these partial dividing walls and the rear upstanding wall and the area therebetween has been completely removed. The spring support 46 has the rear side out off so that there is access to movable contact 48 which must be bent for dummy load adjustment. Load and wear allowance adjustment at the contact making end of the movable contact is made by adjusting stationary contact 60. With the posts 44a being fixed at the dummy load end of the movable contact, bending is the only means of adjustment.

It will be seen in FIG. 6 that the right air gap of the operating magnet is normally closed and the armature is held down by the permanent magnet. Consequently, the movable contacts are separated from the stationary contacts. When the coil is energized, the left end of the armature snaps down against its pole piece to close the contacts. In this condition, the movable contacts separate slightly from bar 40b of the contact support as springs 38 are compressed, thus providing the contacts with a substantial amount of wear allowance.

From the foregoing, it will be apparent that the movable contact structure mounted on the armature in combination with the stationary contact structure, operating magnet and dummy loading on the singlethrow version afford an improved relay -of reduced overall size and efficient operation and ease of assembly in subassembly units as hereinbefore described.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiments of electromagnetic relay disclosed, inasmuch as they are susceptible of various modifications without departing from the scope of the appended claims.

We claim:

1. In a relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising:

an insulating base;

stationary contact means mounted on the interior side of said base and having terminal means on the exterior side of said base for connection to an external circuit;

a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a pair of side members spaced on opposite sides of said center member, one of said side members comprising said permanent magnet;

a rockable armature between said magnetic structure and said base pivoted at its center on said center member with its ends overlying said side members for rocking movement to one of its operating positions when said electromagnet is energized and for return to its other operating position with equal force under the control of said permanent magnet when said electromagnet is deenergized;

movable contact means having contacting portions for engaging said stationary contact means;

terminal means on said base flexibly connected to said movable contactmeans;

and mounting means for said movable contact means comprising:

an insulating spring support on said armature;

compression spring means on said spring support;

said movable contact means overlying said compression spring means;

an insulating contact support overlying said movable contact means;

lateral ears on said movable contact means adjacent said contacting portions thereof;

spaced bars on said insulating contact support overlying said lateral ears, said lateral ears separating from said spaced bars when said armature closes said movable contact means causing compression of said spring means, and said spaced bars imparting a hammer blow to said lateral ears to forcibly separate said contact means when said armature opens said movable contact means;

and means securing said contact support and said spring support to said armature while affording partial compression of said spring means to afford initial bias of said movable contact means against said contact support to reduce contact bounce.

2. The invention defined in claim 1, wherein:

said movable contact means comprises an elongated strip having a contacting portion at at least one end thereof for engaging said stationary contact means;

said compression spring means comprises at least one helical compression spring between said elongated strip and said spring support;

and said contact support comprises two spaced portions bearing down on said elongated strip on opposite sides of said helical compression spring partially compressing the latter to afford initial contact pressure.

3. The invention defined in claim 2, wherein:

said spring support is provided with a shallow recess forming a retaining seat for the lower end of said helical compression spring;

and said elongated strip is provided with a short projection entering the upper end of said helical compression spring serving as retention means.

4. The invention defined in claim 1, wherein:

said base comprises a pair of terminals for connecting the operating coil of said electromagnet to an external circuit.

5. The invention defined in claim 1, wherein:

said relay comprises three subassemblies including:

the base subassembly having the stationary contact means and terminal means;

the operating mechanism subassembly having the electromagnet and the permanent magnet;

and the armature subassembly having the movable contact means and associated mounting means; said electromagnet and armature comprising means for mounting the armature for pivotal movement; and integral mounting studs on said base to which said operating mechanism is secured by screws or the like to attach the three subassemblies together.

6. The invention defined in claim 1, wherein:

said spring support and said contact support comprise walls and interfitting portions affording compartments for the contacting portions of the movable contacts substantially insulated from one another.

7. In a plural-pole double-throw relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising:

an insulating base;

a housing adapted to be secured to said base to enclose the relay mechanism;

two rows of stationary contacts mounted on the interior side of said base within said housing and having integral terminals extending through said base to the exterior side thereof for connection to an external circuit;

a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a pair of side members spaced on opposite sides of said center member, one of said side members comprising said permanent magnet;

a rockable armature between said magnetic structure and said base pivoted at its center on said center member for rocking movement to one of its operating positions when said electromagnet is energized and for return to its other operating position under the force of said permanent magnet when said electromagnet is deenergized;

double-ended movable contacts, each being mounted at its center portion and having a contacting portion at each end for engaging a stationary contact in each said row;

terminals extending through said base flexibly connected to said movable contacts;

and mounting means for said movable contacts comprising:

a pair of coil springs for each movable contact;

and clamping means securing said movable contacts and their associated pairs of coil springs to said armature with each pair of coil springs being in partial compression under their associated movable contact to provide initial contact pressures at both ends of the throw.

8. The invention defined in claim 7, wherein:

each said movable contact is provided with an upward offset at its central portion under which said pair of coil springs are retained in spaced apart relation;

and said clamping means presses down on each movable contact on opposite sides of said offset.

9. In a plural-pole single-throw relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising:

an insulating base;

a housing adapted to be sealed to said base to enclose the relay mechanism;

a row of stationary contacts mounted on the interior side of said base within said housing and having integral terminals extending through said base for connection to an external circuit;

a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a pair of side members spaced apart on opposite sides of said center member, one of said side members comprising said permanent magnet;

a rockable armature between said magnetic structure and said base pivoted at its center on said center member for rocking movement to its operating position when said electromagnet is energized and for return to its restored position under the force of said permanent magnet when said electromagnet is deenergized;

elongated movable contacts having contacting portions at one end arranged to engage the respective stationary contacts in the operating position of said armature;

a row of terminals extending through said base and flexibly connected to said movable contacts;

integral studs on said base arranged to be engaged by the other ends of said movable contacts to serve as a dummy load affording equal contact forces at both ends of the throw;

and mounting means for said movable contacts comprising:

only one coil spring for each movable contact;

and means clamping said movable contacts and their associated coil springs to said armature with the coil spring of each contact being in partial compression under its movable contact to provide initial contact pressure.

10. The invention defined in claim 9 wherein:

each said movable contact is provided with an upward offset at its central portion under which its coil spring is retained at a point nearest its contacting end;

and said clamping means presses down on each movable contact on opposite sides of said offset. 

1. In a relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising: an insulating base; stationary contact means mounted on the interior side of said base and having terminal means on the exterior side of said base for connection to an external circuit; a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a pair of side members spaced on opposite sides of said center member, one of said side members comprising said permanent magnet; a rockable armature between said magnetic structure and said base pivoted at its center on said center member with its ends overlying said side members for rocking movement to one of its operating positions when said electromagnet is energized and for return to its other operating position wiTh equal force under the control of said permanent magnet when said electromagnet is deenergized; movable contact means having contacting portions for engaging said stationary contact means; terminal means on said base flexibly connected to said movable contact means; and mounting means for said movable contact means comprising: an insulating spring support on said armature; compression spring means on said spring support; said movable contact means overlying said compression spring means; an insulating contact support overlying said movable contact means; lateral ears on said movable contact means adjacent said contacting portions thereof; spaced bars on said insulating contact support overlying said lateral ears, said lateral ears separating from said spaced bars when said armature closes said movable contact means causing compression of said spring means, and said spaced bars imparting a hammer blow to said lateral ears to forcibly separate said contact means when said armature opens said movable contact means; and means securing said contact support and said spring support to said armature while affording partial compression of said spring means to afford initial bias of said movable contact means against said contact support to reduce contact bounce.
 2. The invention defined in claim 1, wherein: said movable contact means comprises an elongated strip having a contacting portion at at least one end thereof for engaging said stationary contact means; said compression spring means comprises at least one helical compression spring between said elongated strip and said spring support; and said contact support comprises two spaced portions bearing down on said elongated strip on opposite sides of said helical compression spring partially compressing the latter to afford initial contact pressure.
 3. The invention defined in claim 2, wherein: said spring support is provided with a shallow recess forming a retaining seat for the lower end of said helical compression spring; and said elongated strip is provided with a short projection entering the upper end of said helical compression spring serving as retention means.
 4. The invention defined in claim 1, wherein: said base comprises a pair of terminals for connecting the operating coil of said electromagnet to an external circuit.
 5. The invention defined in claim 1, wherein: said relay comprises three subassemblies including: the base subassembly having the stationary contact means and terminal means; the operating mechanism subassembly having the electromagnet and the permanent magnet; and the armature subassembly having the movable contact means and associated mounting means; said electromagnet and armature comprising means for mounting the armature for pivotal movement; and integral mounting studs on said base to which said operating mechanism is secured by screws or the like to attach the three subassemblies together.
 6. The invention defined in claim 1, wherein: said spring support and said contact support comprise walls and interfitting portions affording compartments for the contacting portions of the movable contacts substantially insulated from one another.
 7. In a plural-pole double-throw relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising: an insulating base; a housing adapted to be secured to said base to enclose the relay mechanism; two rows of stationary contacts mounted on the interior side of said base within said housing and having integral terminals extending through said base to the exterior side thereof for connection to an external circuit; a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a paIr of side members spaced on opposite sides of said center member, one of said side members comprising said permanent magnet; a rockable armature between said magnetic structure and said base pivoted at its center on said center member for rocking movement to one of its operating positions when said electromagnet is energized and for return to its other operating position under the force of said permanent magnet when said electromagnet is deenergized; double-ended movable contacts, each being mounted at its center portion and having a contacting portion at each end for engaging a stationary contact in each said row; terminals extending through said base flexibly connected to said movable contacts; and mounting means for said movable contacts comprising: a pair of coil springs for each movable contact; and clamping means securing said movable contacts and their associated pairs of coil springs to said armature with each pair of coil springs being in partial compression under their associated movable contact to provide initial contact pressures at both ends of the throw.
 8. The invention defined in claim 7, wherein: each said movable contact is provided with an upward offset at its central portion under which said pair of coil springs are retained in spaced apart relation; and said clamping means presses down on each movable contact on opposite sides of said offset.
 9. In a plural-pole single-throw relay of the type having an operating mechanism to afford equal forces at both ends of the actuating movement, the improvement comprising: an insulating base; a housing adapted to be sealed to said base to enclose the relay mechanism; a row of stationary contacts mounted on the interior side of said base within said housing and having integral terminals extending through said base for connection to an external circuit; a magnetic structure comprising an electromagnet and a permanent magnet connected to said base, said electromagnet comprising a magnetic frame and an operating coil thereon, said magnetic frame comprising a center member and a pair of side members spaced apart on opposite sides of said center member, one of said side members comprising said permanent magnet; a rockable armature between said magnetic structure and said base pivoted at its center on said center member for rocking movement to its operating position when said electromagnet is energized and for return to its restored position under the force of said permanent magnet when said electromagnet is deenergized; elongated movable contacts having contacting portions at one end arranged to engage the respective stationary contacts in the operating position of said armature; a row of terminals extending through said base and flexibly connected to said movable contacts; integral studs on said base arranged to be engaged by the other ends of said movable contacts to serve as a dummy load affording equal contact forces at both ends of the throw; and mounting means for said movable contacts comprising: only one coil spring for each movable contact; and means clamping said movable contacts and their associated coil springs to said armature with the coil spring of each contact being in partial compression under its movable contact to provide initial contact pressure.
 10. The invention defined in claim 9 wherein: each said movable contact is provided with an upward offset at its central portion under which its coil spring is retained at a point nearest its contacting end; and said clamping means presses down on each movable contact on opposite sides of said offset. 